1. Technical Field
This invention relates to a composite trailer and van type container for transportation and management of bulk freight, and more particularly to the fabrication of these trailers and containers using both steel and aluminum components. This fabrication, therefore, requires the joining of dissimilar materials in a strong durable joint.
2. Background of the Invention
Using different composite materials in the construction of tractor trailers, as well as van type containers used for transportation and management of bulk freight, would be preferred over the traditional construction generally comprising either all steel or all aluminum. Trailers or van type containers constructed of all steel are generally heavier, thereby reducing the amount of allowable payload, while trailers and containers constructed of all aluminum are generally more expensive and often not as structurally reliable since aluminum is not as durable by volume as structural steel.
However, trailers and containers used for hauling bulk freight which are constructed of dissimilar composite metals are even less reliable. The metalurgical incompatibilities between the joints of dissimilar metals prevent direct welding. Therefore, the use of mechanical fasteners such as bolts and brackets are used. These techniques often fail when exposed to the hazards of the road and the environment. For example, the different metallurgical properties, including the rate of flexibility between aluminum alloys and ferrous metals, cause the fasteners to work loose. Further, corrosion and galvanic reactions between dissimilar trailer and container metal components tend to shorten its useful life by premature failure at the joining interface. This is particularly true in the case of attaching steel components to aluminum components used in trailer construction.
In the past, the assembly of steel to aluminum parts has been tried using an insulating barrier between these metals to try to reduce galvanic corrosion. Even with this special assembly, however, some dissimilar metal contact occurs since it is necessary to make the connection of the two dissimilar metal parts with fasteners of one material or the other, as previously described. Therefore, the probability of a galvanic reaction causing electrolytic corrosion has always been unavoidable using this technique for the fabrication of tractor trailers since it is virtually impossible to effect a perfect insulating barrier between the dissimilar metals.
Other structures with composite metals have used a variety of different joining techniques in an attempt to improve the reliability between the interface; See for example U.S. Pat. Nos. 4,281,235, 3,975,612, 3,872,577, 3,664,816, 3,597,832, 3,460,235, 3,175,284, 3,295,197 and 3,100,338. Additionally, U.S. Pat. Nos. 2,600,140, 2,758,870, 4,212,405 and 4,904,017 can be viewed.
In U.S. Pat. No. 4,281,235, a method for joining ferrous alloys to aluminum and aluminum alloys is accomplished by coating the portion of the ferrous alloys to be welded with an intermediate material compound or element such as gold alloy or silver. The contact area to be joined is then bombarded by an accelerated particle beam to effect the union.
In U.S. Pat. No. 3,975,612 a welding method for dissimilar metals is disclosed wherein a filler metal is deposited an one end of a dissimilar metal and then joined with the other metal which has the same composition as that of the deposited filler material.
In U.S. Pat. No. 3,664,816, a steel to aluminum transition piece is shown in which the transition joint is formed by making a pressure weld between an aluminum alloy and steel through a special aluminous bonding element. The aluminous bonding element is primarily aluminum with the transition material being stainless steel as the steel element.
In U.S. Pat. No. 3,597,832, inertia welding of steel to aluminum is disclosed describing friction welding to join a pair of conical interacting configurations of dissimilar metal. In U.S. Pat. No. 3,175,284, a method of friction welding of dissimilar metals is disclosed in which the surface of one material is rotated relative to the other surface so as to generate heat for the welding process.
In U.S. Pat. No. 3,295,197, the disclosure shows a stainless steel member bonded with an aluminum member in a composite metal configuration. Finally, in U.S. Pat. No. 3,100,338, a method is disclosed for joining aluminum metal to refractory hard metals using a flux composition in the joining process.